using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		 var rx = "[a-zA-Z0-9]N[a-zA-Z0-9]{4}[0-9][a-zA-Z0-9]|([a-zA-Z0-9]{6}[0-9][a-zA-Z0-9])|[a-zA-Z0-9]{6}[a-zA-Z][a-zA-Z0-9]";
		 var results = Regex.Matches("BJX4700QHJ43EKU2KU89EJKM", rx)
		            .Cast<Match>()
		            .Where(m => !m.Groups[1].Success)
		            .Select(z => z.Value);
         foreach (var s in results)
        	Console.WriteLine(s);
	}
}